refactor(input): remove legacy property and support for legacy syntax (#29017)

Issue number: internal

---------

## What is the current behavior?

In Ionic Framework v7, we [simplified the input
syntax](https://ionic.io/blog/ionic-7-is-here#simplified-form-control-syntax)
so that it was no longer required to be placed inside of an `ion-item`.
We maintained backwards compatibility by adding a `legacy` property
which allowed it to continue to be styled properly when written in the
following way:

```html
<ion-item>
  <ion-label>Label</ion-label>
  <ion-input></ion-input>
</ion-item>
```

While this was supported in v7, console warnings were logged to notify
developers that they needed to update this syntax for the best
accessibility experience.

## What is the new behavior?

- Removes the `legacy` property and support for the legacy syntax.
Developers should follow the [migration
guide](https://ionicframework.com/docs/api/input#migrating-from-legacy-input-syntax)
in the input documentation to update their apps. The new syntax requires
a `label` or `aria-label` on `ion-input`:
    ```html
    <ion-item>
      <ion-input label="Label"></ion-input>
    </ion-item>
    ```
- Removes the legacy tests under under `input/test/legacy/` and all
related screenshots
- Removes the input usage from `item/test/a11y`, `item/test/counter`,
`item/test/disabled`, `item/test/highlight`,
`item/test/legacy/alignment`, `item/test/legacy/disabled`,
`item/test/legacy/fill`, and `item/test/legacy/form` and all related
screenshots if the test was removed

## Does this introduce a breaking change?

- [x] Yes
- [ ] No

1. Developers have had console warnings when using the legacy syntax
since the v7 release. The migration guide for the new input syntax is
outlined in the [Input
documentation](https://ionicframework.com/docs/api/input#migrating-from-legacy-input-syntax).
2. This change has been documented in the Breaking Changes document with
a link to the migration guide.

BREAKING CHANGE:

The `legacy` property and support for the legacy syntax, which involved
placing an `ion-input` inside of an `ion-item` with an `ion-label`, have
been removed from input. For more information on migrating from the
legacy input syntax, refer to the [Input
documentation](https://ionicframework.com/docs/api/input#migrating-from-legacy-input-syntax).

---------

Co-authored-by: ionitron <hi@ionicframework.com>

packages/angular/src/directives/proxies.ts

@@ -955,7 +955,7 @@ export declare interface IonInfiniteScrollContent extends Components.IonInfinite
 
 
 @ProxyCmp({
-  inputs: ['autocapitalize', 'autocomplete', 'autocorrect', 'autofocus', 'clearInput', 'clearOnEdit', 'color', 'counter', 'counterFormatter', 'debounce', 'disabled', 'enterkeyhint', 'errorText', 'fill', 'helperText', 'inputmode', 'label', 'labelPlacement', 'legacy', 'max', 'maxlength', 'min', 'minlength', 'mode', 'multiple', 'name', 'pattern', 'placeholder', 'readonly', 'required', 'shape', 'spellcheck', 'step', 'type', 'value'],
+  inputs: ['autocapitalize', 'autocomplete', 'autocorrect', 'autofocus', 'clearInput', 'clearOnEdit', 'color', 'counter', 'counterFormatter', 'debounce', 'disabled', 'enterkeyhint', 'errorText', 'fill', 'helperText', 'inputmode', 'label', 'labelPlacement', 'max', 'maxlength', 'min', 'minlength', 'mode', 'multiple', 'name', 'pattern', 'placeholder', 'readonly', 'required', 'shape', 'spellcheck', 'step', 'type', 'value'],
   methods: ['setFocus', 'getInputElement']
 })
 @Component({
@@ -963,7 +963,7 @@ export declare interface IonInfiniteScrollContent extends Components.IonInfinite
   changeDetection: ChangeDetectionStrategy.OnPush,
   template: '<ng-content></ng-content>',
   // eslint-disable-next-line @angular-eslint/no-inputs-metadata-property
-  inputs: ['autocapitalize', 'autocomplete', 'autocorrect', 'autofocus', 'clearInput', 'clearOnEdit', 'color', 'counter', 'counterFormatter', 'debounce', 'disabled', 'enterkeyhint', 'errorText', 'fill', 'helperText', 'inputmode', 'label', 'labelPlacement', 'legacy', 'max', 'maxlength', 'min', 'minlength', 'mode', 'multiple', 'name', 'pattern', 'placeholder', 'readonly', 'required', 'shape', 'spellcheck', 'step', 'type', 'value'],
+  inputs: ['autocapitalize', 'autocomplete', 'autocorrect', 'autofocus', 'clearInput', 'clearOnEdit', 'color', 'counter', 'counterFormatter', 'debounce', 'disabled', 'enterkeyhint', 'errorText', 'fill', 'helperText', 'inputmode', 'label', 'labelPlacement', 'max', 'maxlength', 'min', 'minlength', 'mode', 'multiple', 'name', 'pattern', 'placeholder', 'readonly', 'required', 'shape', 'spellcheck', 'step', 'type', 'value'],
 })
 export class IonInput {
   protected el: HTMLElement;